Noh-Seok Kwak

The synthesis of poly(vinylphosphonic acid-co-methacrylic acid) microbeads by suspension polymerization and the characterization of their indium adsorption properties.

Poly(vinylphosphonic acid-co-methacrylic acid) microbeads were synthesized by suspension polymerization, and their indium adsorption properties were investigated. The obtained microbeads were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). The microbeads were wrinkled spheres, irrespective of the components, and their sizes ranged from 100 to 200 μm. The microbeads were thermally stable up to 260°C. As the vinylphosphonic acid (VPA) content was increased, the synthetic yields and ion-exchange capacities decreased and the water uptakes increased. The optimum synthetic yield, ion-exchange capacity and water uptake were obtained at a 0.5 mol ratio of VPA. In addition, the maximum adsorption predicted by the Langmuir adsorption isotherm model was greatest at a 0.5 mol ratio of VPA.

Synthesis and Characterization of EFFE-g-(VBTAC-co-HEMA) Anion Exchange Membranes Prepared by a 60Co Radiation-Induced Graft Copolymerization for Redox-Flow Battery Applications

AbstractVinyl benzyl trimethyl ammonium chloride (VBTAC) was grafted onto poly(ethylene-co-tetrafluoroethylene) (ETFE) film by γ-ray using simultaneous irradiation graft copolymerization in the presence of 2-hydroxyl ethyl methacrylate (HEMA). The structure of the ETFE-g-(VBTAC-co-HEMA) anion membrane was confirmed by Fourier transform infrared spectroscopy and thermogravimetric analysis. The degree of grafting (DG) of the membrane increased with total irradiation dose and VBTAC monomer concentration. The highest DG of an ETFE-g-(VBTAC-co-HEMA) membrane was 92%, which was synthesized by the treating of an ETFE film with a 0.8 M solution of VBTAC monomer in the presence of 50 kGy irradiation. Different properties of the anion membrane, such as water uptake and ion exchange capacity, increased as DG increased. The permeability and vanadium redox-flow battery performance were measured for a membrane with a DG of 92%. The average voltage efficiency, coulombic efficiency, and energy efficiency were 0.79, 0.88, and 0.70, respectively, all of which remained stable as the number of cycles increased.

Synthesis and characteristics of UV curable dimethyl 5-sulfoisophthalate sodium salt-co-diethylene glycol with maleic and phthalic anhydride copolymers (DMSIP-co-DEG-co-MA/PA) for application in redox flow batteries

AbstractDimethyl 5-sulfoisophthalate sodium salt (DMSIP)-co-diethylene glycol (DEG)-co-maleic anhydride (MA)/phthalic anhydride (PA) oligomers were synthesized via condensation reaction and the corresponding membranes were prepared by UV curing. The number-average molecular weight (Mn) of the DMSIP-co-DEG-co-MA/PA (DDMP) was proportional to the concentration of DMSIP and ranged from 1,360–2,856 g/mol. A successful introduction of a -SO3Na group to the main oligomer chain was confirmed using Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopy and the thermal stability of the membranes up to 300 °C was analyzed using thermogravimetric analysis (TGA). The water uptake values, swelling ratios, and the ion-exchange capacities of the membranes were 13%–30%, 7%–15%, and 0.7–0.9 meq/g, respectively. The electrical properties of the membrane, including the area resistance, ion transport number, and the cyclic charge-discharge current were also analyzed; these properties confirmed that these membranes were suitable for use in redox flow battery (RFB) applications.

Characteristics of HfO 2 Thin Films Using Wet Etching

Hafnium oxide () was very advantageous for substitute material of gate on existing transistor. has been widely studied due to high contact with polysilicon and thermal stability and also, it is easily etched by using HF solution. In this study, and thermal oxide films were etched by wet etch method using chemical etchant. Etch rate of and thermal oxide was linearly increased with increasing concentration of HF and temperature but etch rate of was higher than thermal oxide due to , , and ions at below 0.5% concentration of HF. And also, etch selectivity was improved by adding Hydrazine as additive.